Advances in technology have enabled the size of personal computers to decrease. As a result, the use of portable computers, such as notebook computers, laptop computers, and notepad computers, is rapidly increasing. The portability of notebook computers and notepad computers enables a user to keep his or her computer readily accessible such that computing resources are effectively always at hand. FIG. 1 illustrates a typical notebook computer with two folding halves, with a display portion in one half and an input portion in the other half. The display portion includes a display bezel that frames a display screen. The input portion includes among other things, a keyboard for inputting data and a touchpad for navigating a cursor control.
The usability of notebook computers depends largely on the life of the power source (i.e., battery pack). When inactive for a certain period of time, or when the display portion is closed over the keyboard section, most notebook computers have a “sleep mode” feature that turns off most of the power consuming components (e.g., monitor, hard disk) while using minimal power to conserve memory in order to “wake up” the notebook computer again. Notebook computers typically have two types of sleep mode: standby and hibernation. In standby mode, the “state” of the notebook computer (programs that are running and data in memory) is copied into an area of the notebook computer's memory that stays alive while the notebook computer is standing by. The hard drive, monitor and other components are turned off, but a very small amount of power is used to keep the memory alive so that it can store the data it needs when the notebook computer wakes up. In hibernation mode, instead of writing the state of the notebook computer into memory, it copies it to the hard drive and then shuts the computer off completely.
When the display portion of a notebook computer is closed over the keyboard section, two common mechanisms detect the notebook computer in a closed configuration and actively trigger the sleep mode. As illustrated in FIG. 1, in one mechanism, a mechanical switch disposed near an edge of the input portion is depressed to activate the sleep mode. In a second mechanism, sensors are disposed on both the display and input portions that detect each other in the closed position. For example, a magnet may be disposed within the bezel of the display portion and a magnet sensor may be disposed within the body of the input portion. When in close proximity, the sensor detects the magnet disposed within the bezel, and the sleep mode is activated. The use of magnet sensors is known as Hall Effect magnet sensors.
One problem with these detecting mechanisms is that is that they contribute significantly to the manufacturing cost of notebook computers. Another problem is that sensors, magnet sensors in particular, are difficult to assemble into notebook computers because they add a level of unwanted complexity.